Acid Gas to Acid By Wet Process Technology

Company Profile

Ningbo Far-east Chemical Group Co., LTD. is located in Ningbo, a coastal open city with booming economy, Far-east Group is a high-tech enterprise integrating research and development of new chemical technology and new process, research and development of catalyst, process package development, research and development and application of new energy (lead carbon battery, lithium battery, charging pile).In 2011, Far-east Group was awarded the title of "national high-tech enterprise" with several branch companies.

Adhering to the business philosophy of people-oriented, integrity and win-win, and scientific and technological innovation, the company is committed to making due contributions to the development of coal chemical industry.

Core Technology

Coal Tar Hydrogenation

Ethylene Glycol

New Energy Battery.Charging Pile

Sulfur Recovery Technology

Acid Gas to Acid By Wet Process

Quality Comes From Trust

Innovation Contributes To The Future

Enterprise mission:

Focus on energy and environment, provide high quality process package and technical services, and constantly strive to create value

Corporate vision:

To be the most innovative and R&D capable provider in China

 

Honor

Acid Gas to Acid By Wet Process Technology

Characteristics Of Acid Gas To Acid By Wet Process

(1)The device has high operating flexibility and is easy to maintain.

(2) Loose control of sulfur and oxygen ratio, without precise control of H2S/SO2 ratio, simple and short process, less equipment, small footprint, adopting DCS control and easy operation.

(3)Localization of all equipment and complete elimination of acid corrosion of key equipment.

(4)in the catalytic transformation process of SO2, the amount of air is small, and the temperature of the catalyst bed is controllable. Interlayer cooling is adopted to improve the conversion rate of SO2 and reduce the content of SO2 in the exhaust gas.

(5)simple operation and control, without drying treatment for the process gas, high acid concentration, up to 99.5%. 

(6)Low operating cost, and long service time of the catalyst

(7)Byproduct of high quality steam, with high energy utilization efficient.

(8)The content of SO2 in exhaust gas is less than 35mg/cubic meters, reaches the current emission regulations.

Brief introduction of the process

Acid Gas Combustion

SO₂ Catalytic Oxidation

SO₃ Synthesis Sulfur Acid

Heat Recovery

Process Flow

Acid Gas to Acid By Wet Process-Acid Gas Combustion

H₂S Combustion Reaction

 

 

Acid gas from the bounds sends to the combustion furnace to react(combustion reaction temperature (950-1050 ℃), H2S, COS, CS2 generating SO2, and releasing a lot of heat. The heat generated from the combustion is recovered by the waste boiler behind the combustion furnace, producing saturated medium pressure steam.

    H2S in acidic gas is peroxide combustion, and the proportion of combustion-supporting air is about 1.5-2.2 times of chemical equivalent, keeping the furnace in an oxidizing atmosphere, which is conducive to promoting the full reaction of various impurities in acidic gas (such as COS).

Features of Supporting Acid Gas Combustor

Ø  Horizontal type side-burning high strength premix combustor  is used to set in the mixing section and wind swirling blades. The gas is mixed evenly and the acid gas is burned fully

Ø  With special materials and unique structure design, the service life of combustor nozzle is guaranteed to exceed five years

Ø  The combustor has wide load adjustment range, and the combustion medium has strong adaptability

SO₂ Catalytic Oxidation :

 The process gas after heat recovery by waste boiler heat (temperature at 410-415 ℃)  is sent into the catalytic oxidation reaction section, under the effect of wet sulfuric acid catalyst, SO2 transforms to SO3 by the catalytic oxidation. The reaction heat produced by the catalytic reaction section is used to overheat the medium pressure saturated steam produced by the superheating device.

The reaction is exothermic reaction, which is affected by the reaction equilibrium. the reaction temperature is high, the reaction speed is fast and the efficiency is high, but the equilibrium conversion rate is low. Therefore, controlling the reaction temperature is helpful to improve the equilibrium conversion rate and  the overall conversion rate.

 

Gas  entering into the SO2 catalytic reactor is about 410 ℃, the reactor is divided into three catalytic reaction stages:

Ø  The gas temperature entering the three catalysts bed is controlled by three independent cycles.

Ø  The temperature entering the first bed is controlled by the internal bypass of the waste heat boiler.

Ø  The inlet temperature of the second bed is controlled by the steam flow of the first bed heat exchanger.

Ø  The inlet temperature of the third bed is controlled by the steam flow of the second bed heat exchanger.

Ø  The outlet temperature of the process gas cooler is strictly controlled , in order to make sure that the temperature entering into the downstream sulfuric acid vapor condenser is not higher than 300 ℃.

SO3 firstly combines with water vapor to form sulfuric acid steam and then condenses, gaseous sulfuric acid condenses into liquid sulfuric acid and separates from other gases. The equilibrium conversion and reaction speed of SO3 water forming sulfuric acid vapour is influenced by the temperature of non-condensable gas concentration in the gas phases, sulfuric acid vapor condenses generally from the beginning of the 240-260 ℃ and ends at the temperature  about the 160-170 ℃.

 

Acid Gas to Acid By Wet Process-Heat Recovery

Ø      The process gas leaves the catalytic reaction which cooling to about 280 ℃ by the gas cooler  and then enters into the sulfuric acid vapor condenser and produces saturated steam. The hot process gas goes into the sulfuric acid steam condenser, exchanging heat with the air and further reduce the temperature, dropping to 100 ℃, prompting SO3 and water in the process gas to the sulfuric acid by hydration and sulfuric acid coagulates on vertical glass tube wall of the condenser. The sulfuric acid condenses into drops and falls on the bottom of the condenser by gravity.

Ø  Without special measures, some of the sulfuric acid steam will condense into tiny droplets of sulfuric acid. Some of the acid mist particles are too small to separate from the process. In order to reduce the fine acid fog in the exhaust gas, we set up a multi-layer defogging devices.

Ø  The steam is produced in two parts of the device, a waste heat boiler and a process

gas cooler, which are simultaneously connected to a medium-pressure steam drum. The medium-pressure steam coming from the drum passes through the cooler between first and second bed and becomes superheated steam to be sent out of the boundary area.

Ø  Control the steam drum pressure 4.5 MPa(G) (257 ℃), to ensure that the temperature of the boiler water sufficiently higher than the dew point of the process air.

Ø  temperature of process gas in the heat exchanger between the beds is controlled by steam bypass.

Main equipment: combustion furnace, SO2 converter, sulfuric acid steam condenser, etc., covering an area of 600-700m2

Core Equipment

Ø  Combustion furnace (supporting)

The number and specifications of fuel nozzles is  according to the actual requirements, the combustion chamber is lined with firebrick, The shell can be either cold or hot type as required

Ø  Sulfuric acid condenser (self-developed)

Sulfuric acid condenser is made up of vertical glass tube which is resistant to acid and high temperature. The tubeplate material is carbon steel outer-lining fluorinated polymer. The bottom of the condenser is lined with acidproof bricks and insulation bricks. The top of the condenser is anti-corrosive with acidproof coating. Both shell and baffle are made of carbon steel.

The condenser has been designed, manufactured and maintained domestically, with low investment cost.

List Of Core Equipment

 

 

Operational consumption of  sulfuric acid by wet process

Item name	Fareast Tech
Sulfuric acid concentration%	98
Sulfuric acid production t/h	3.25
Steam  t/h	6.27
Recirculated cooling water t/h	24.5
Boiler feed water t/h	6.3
Power consumption KWh	265.2
Catalyst life time	5-8
Sulfur recovery rate %	99
Investment /Ten thousand yuan	4000

n  The actual case of acid gas to acid process:

n  Flow:2304m³/h.H₂S30.28%(mol).CO₂62.89%.N₂2.67%.

n  Scale:26000t/a sulfuric acid

 

Process controlling

n  Adjusting the excess air, controlling the furnace temperature in 950-1050 ℃ steadily relying on fuel gas, to ensure the gas combust completely to SO2, and control the air temperature above 250 ℃ into the furnace, raise the utilization ratio of heat.

n  Ensuring the temperature of the mixing air into the inverting oxidation device is stable, and the temperature is regulated by the outlet of waste heat boiler and the auxiliary line of combustion furnace.

n  The control of interlayer temperature depends on the regulation of air intake and heat exchanger steam.

n  Setting the temperature limit alarm in the furnace and at the inlet of the converter

n  The outlet temperature of the acid condenser is adjusted by the flow of cold air, and steam heating is set to heat the cold air.

n  Since the dew point temperature of the reaction gas should be ensured to avoid corrosion, the pressure of the gas drum of the boiler should be above 4.5mpa (G).Set up the control device at the steam outlet of the gas drum, according to the customer's demand for steam temperature and pressure.

 

The Scale Of Acid Gas To Acid By Wet Process

There will be sulfide acidic gas such as H2S in chemical fertilizer, oil, petrochemical, metallurgical, coal chemical industry , so sulfuric acid by wet process should be used in these industries to deal with acidic gas, it is not only reduces the pollution to the environment, but also increases economic profit of the enterprises, realizing green and clean to the industry .Sulfuric acid can be directly produced from acidic gas in chemical fertilizer plant, oil refinery, methanol plant, coking plant and power plant, that the process has great application prospect

 

Patent Technology

The patent for acid gas to acid by wet process has been applied:

Ø  A system for producing sulfuric acid by acidic gas (utility model, application number 201720413058.8)

Ø  A system for continuous and stable production of high concentration sulfuric acid by acidic gas (utility model, application no. 20172041155.9)

Typical application

Ø  China Molybdenum Co., Ltd. 

•       Project description: maintenance and renovation of sulfuric acid steam condenser in acid gas sulfuric acid plant

•       Sulfuric acid steam condenser: 98% sulfuric acid capacity 24000t/a

•       Emission exhaust: SO2<30mg/cubic meters and acid fog <5mg/cubic meters

Ø  Shandong Ruixing Chemical Industry Group

Ø  Sulfuric acid by wet process

•       Industry: coal chemical industry

•       Project description:

       Process design for the expansion and transformation of the sulfuric acid by wet process device, and provide the core equipment - sulfuric acid steam condenser

•       Design parameters:

Item	Acid gas flow Nm3/h	H2S concentrate mol%	Acid production t/d	High pressure steam t/d
Index	3300	22	70	186